New NOAA Precipitation Frequency Estimates for Iowa Now Available

Interests in private industry, government and academia have eagerly awaited the publication new precipitation frequency estimates for Iowa as well as sixteen other midwestern and southeastern states. Those estimates were published by the NWS Office of Hydrologic Development on April 19th as Volumes 8 and 9 of NOAA Atlas 14, a wholly web based publication available at http://www.nws.noaa.gov/oh/hdsc . The last time that these estimates were updated was in 1963.

Precipitation frequency estimates are estimates of climate variability. They are used as design standards for civil infrastructure built to cope with rainfall and runoff such as storm water drainage systems, roads, bridges, culverts, small dams, roofs, airport runways, in-stream ecosystems including fish habitat, stream erosion control, pollution control systems, flood insurance rate maps, soil conservation, etc. These new estimates directly contribute to the preparation of more cost effective designs, plans, maps, etc.; protecting lives and property and preventing pollution.

NWS precipitation frequency estimates--prepared since the 1950s--are cited as design standards in many Federal, State and Local Government regulations. These new NOAA Atlas 14 Volumes will result in new design criteria for a large range of engineering and planning projects across seventeen states. Those states are indicated by the red shading (for NOAA Atlas 14, Volume 8) and the blue shading (for NOAA Atlas 14, Volume 9) in Figure 1 below.

Figure 1. Map showing the states that are included the newly updated NOAA precipitation frequency estimates. The red shading indicates states included in NOAA Atlas 14, Volume 8. The blue shading indicates states included in NOAA Atlas 14, Volume 9. Iowa is included in Volume 8. For more information see http://www.nws.noaa.gov/oh/hdsc/ .